As hydraulic hoses and high pressure hoses (hereinafter, collectively referred to as “hydraulic hoses” or the like) that are used in various industrial purposes, hoses having a configuration, in which a reinforcing layer formed by braiding reinforcing yarn and steel wire is provided in between a rubber layer and another rubber layer so that functions as a hose can be maintained without causing liquid leakage or the like even in a severe environment involving great fluctuations in temperature and/or pressure, have been known. To enhance the adhesion to a rubber layer, such a reinforcing layer is used after, for example, its surface is plated with a metal such as brass.
Japanese Unexamined Patent Application Publication No. 2002-13083A describes a rubber composition that contains a rubber component and a porous inorganic filler and that enhances the adhesion of a brass-plated reinforcing layer and a rubber layer by releasing moisture during vulcanization.
However, the rubber composition described in Japanese Unexamined Patent Application Publication No. 2002-13083A cannot maintain water content that is necessary during vulcanization because of vaporization of moisture during storage for a long period of time, and as a result, the adhesion between the rubber layer and the reinforcing layer may decrease. In particular, when vulcanization is performed by an oven vulcanization method, which is a continuous vulcanization method, to enhance productivity, vaporization of moisture during vulcanization is remarkable and it may not be possible to achieve sufficient adhesion between the rubber layer and the reinforcing layer. Therefore, a rubber composition having good adhesion to a metal-plated reinforcing layer has been desired.